Apache Zookeeper Ensemble on Local Machine
Setting up a Zookeeper Ensemble
The instructions are for simulating the set up of ensemble on a single machine. However with just the change in port numbers we can set it up on different machines in production.
Number of Zookeeper Servers
The number of zookeeper servers are usually odd. The ensemble is of size 3 in this example.For more information on the number of ZK servers read here Setting up External Zookeeper Ensemble
Steps to create Ensemble
- Create directories for Zookeeper server installation for 3 Zookeepers
mkdir -p $HOME/zookeeper/zk1 $HOME/zookeeper/zk2 $HOME/zookeeper/zk3
- Create data directories for 3 Zookeepers
mkdir -p $HOME/zookeeper/data/zk1 $HOME/zookeeper/data/zk2 $HOME/zookeeper/data/zk3
- Create Log directories for 3 Zookeepers
mkdir -p $HOME/zookeeper/log/zk1 $HOME/zookeeper/log/zk2 $HOME/zookeeper/log/zk3
- Create myid for each Zookeeper Server
vi $HOME/zookeeper/data/zk1/myid
vi $HOME/zookeeper/data/zk2/myid
vi $HOME/zookeeper/data/zk3/myid
The ID is stored inside the /myid file. The ID identifies each server. So each of the 3 myid files will contain the content 1, 2 and 3. The Id should be between 1 and 255.
- Download Zookeeper and extract
Copy the installation into the respective server directories that were created for each ZK server.
Installtion is available here: Zookeeper Download the latest and most stable release. Version 3.4.4 is used in this exercise.
Assuming your installation resides in the Downloads directory, copy the installation into the respective ZK servers directories:
cp -r ~/Downloads/zookeeper-3.4.4/* $HOME/zookeeper/zk1/
cp -r ~/Downloads/zookeeper-3.4.4/* $HOME/zookeeper/zk2/
cp -r ~/Downloads/zookeeper-3.4.4/* $HOME/zookeeper/zk3/
- Configure the zoo.cfg files for all the Zk servers
zoo.cfg for zk1
vi ~/zookeeper/zk1/conf/zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=$HOME/zookeeper/data/zk1
clientPort=2181
dataLogDir=$HOME/zookeeper/log/zk1
server.1=localhost:2888:3888
server.2=localhost:2889:3889
server.3=localhost:2890:3890
zoo.cfg for zk2
vi ~/zookeeper/zk1/conf/zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=$HOME/zookeeper/data/zk2
clientPort=2182
dataLogDir=$HOME/zookeeper/log/zk2
server.1=localhost:2888:3888
server.2=localhost:2889:3889
server.3=localhost:2890:3890
zoo.cfg for zk1
vi ~/zookeeper/zk1/conf/zoo.cfg
tickTime=2000
initLimit=10
syncLimit=5
dataDir=$HOME/zookeeper/data/zk3
clientPort=2183
dataLogDir=$HOME/zookeeper/log/zk3
server.1=localhost:2888:3888
server.2=localhost:2889:3889
server.3=localhost:2890:3890
Note:
server.X=<IPAddress>:<Port1><Port2>
X = myId of each Zookeeper server
<IPAddress> = This is the HostName of the machine where each Zookeeeper server is running. In our case The entire ensemble is running on 1 machine, so hostname is “localhost”.
<Port1> and <Port2> : Read below:
Each of the servers listen on 3 ports:
1) Port (2181,2182,2183) for client connections
2) Port (2888,2889,2890) for follower connections if they are leaders themselves
3) Port (3888,3889,3890) for listening to other servers during the leader election.
Note: When setting up on different machines all servers can listen on:
Port 2181 for client connections
Port 2888 for follower connections
Port 3888 for listening to other servers.
Since we are simulating the ensemble on the same machine, different ports are used.
- Start Zookeeper servers
Start zk1
$ cd $HOME/zookeeper/zk1/bin/
$ ./zkServer.sh start
Start zk2
$ cd $HOME/zookeeper/zk2/bin/
$ ./zkServer.sh start
Start zk3
$ cd $HOME/zookeeper/zk3/bin/
$ ./zkServer.sh start
- Verify the status of Zookeeper Ensemble
zkServer.sh supports the following commands that could be used to check the status of each ZK server:
1)start
2)start-foreground
3)stop
4)restart
5)status
6)upgrade
7)print-cmd
